The invention relates to a method and a system for diagnosing the operating state of an assisted starting mode of a motor vehicle.
Currently, certain motor vehicles are fitted with an assisted starting mode which consists in managing the parking brake automatically when the vehicle is started. The parking brake is a braking system that supplements the brakes actuated by the brake pedal. This parking brake is usually used to immobilize the vehicle when the latter is stationary, and can also be used to carry out emergency braking when the vehicle is moving.
Automatic management of the parking brake makes it possible, amongst other things, to help the driver to carry out a starting on a slope, also called a “hill start”. The principle of the hill start is to release the brakes on the non-drive wheels when the torque transmitted by the engine to the drive wheels is sufficient to compensate for the effect of the slope.
One of the problems encountered when automatic starting management is used is that this management may, in certain conditions, not request the release of the brakes thus refusing the assisted start.
It is therefore useful to be able to ascertain the conditions that have led to such a refusal for the purpose of diagnosing the possible faults of the automatic starting management system. Also, it may be worthwhile to save the traces of these refusal conditions, but the saves of these conditions may be numerous and occupy considerable memory space. The question is therefore to fit the vehicles with appropriate means for economizing on the memory space used by the saving means.
It is possible to cite for example the British patent application GB 2 376 990 which describes a parking-brake control system in which the parking brake is released when the vehicle is driven in a positive movement and the clutch pedal reaches a satisfactory position, but this document does not describe a means for diagnosing the conditions of refusal of an assisted start.
It is possible to cite also the British patent application GB 2 342 967 which discloses a parking-brake control device in which said brake is released when the braking torque applied to the wheels is below a certain threshold. Moreover, it is possible to cite the French patent application FR 2 828 450 filed in the name of the applicant which describes an assisted hill start device and the French patent application FR 2 841 199, also filed in the name of the applicant, which discloses a device for the automatic release of the automatic parking brake when starting. But these documents also do not disclose a means for diagnosing the conditions of refusal of an assisted start.